Camshafts for a High Compression 2.4S

[Edwin Ek]

What camshafts would you all recommend for my rebuild? The original ones are trash. It's a 73 S motor, all stock except for 2.2 S pistons and cylinders. I've heard talk about 906 camshafts, but don't know whether they are appropriate or not. I'm going to use the car as a fun, every once-in-a-while driver, and I sure like revs

Thanks,
Ed

[gruen911]

Ed
906 cams are big and aggressive, but maybe too big and impractical for weekend street use.
You said you like rev's. Maybe we should differentiate rev's and high end rev's. High end rev's are certainly what you will get with 906 cams. But if you want plenty of rev's, you should consider moving slightly downward and going with Solex cams. They are almost peaky as S cams but more guts at mid range all the way up to redline at around 7,000. Especially with the higher compression 2.2S P&C's, the solex cams will give you a very strong acceleration curve and plenty of top end. Either way you should have a fast driving car, but you will experience more moment to moment power with Solex cams.

[Zeke]

For some reason I don't see a location for either poster. So, I have no idea what kind of gas you can and will buy.

You might want to get each cam's specs and read the overlap. OL will detetmine the dynamic compression. Yours is high to start with.

[Chuck Miller]

Ed,

What I've learned is 906 cams are not the way to go for a MFI engine... 906's can be timed to work GREAT for almost any small high performance CARBED engine.

I would stay with your S cams or go to a WebCam regrind - I put WebCam 120/104's in my 2.4S/2.7RS rebuild and they work GREAT!!!! ...

Cheers,

[obrut]

i've got GE80's in my "improved" 2.7Rs spec engine - less duration than RSR sprint cams but slightly higher lift. They make great power, work well with MFI and aren't too cranky down low.

[Bobboloo]

You need to keep in mind that the torque curve of a given cam moves downward in RPMs when you increase displacement so a GE 80 will not feel the same in a 2.4 motor as it did in a 2.7. Here's a chart that illustrates this point.

As you can see the torque curve moves downward for the same S cam in the 2.7RS motor as compared to the 2.4S.

The solex is a nice compromise between an E and a S but as Milt points out when he mentions octane you might need the extra duration of the S cam to offset the high compression ratio of the 2.2S pistons with a 70.4mm stroke. The solex may be more prone to detonation.

A friend of mine had 906 cams in a 3.2MFI motor and even at that displacement he found them undesirable for the street. I can't imagine what a bear they would be in a 2.4. (visions of a race car with hot cams being helped "i.e. pushed" out of the pits comes to mind.) Okay, maybe I'm exaggerating but you get my point.

[Richard]

I have S cams in my '73 2.4S (stock 8.5 to 1 compression) with MFI. The S cam is a great cam even by modern cam standards. I really like the way it sort of explodes at about 5,000 RPM and puts you back in the seat. They provide plenty torque at lower RPMs in a 2.4L...unless you are planning on using this car as a daily driver in traffic. I have also run a 2.7RS MFI motor in another car with these cams and they were terrific there too but with a little less of a power surge because of the larger 2.7 displacement. I have a '67S built out to 2.2L (stock 9.8 to 1 compression) with Solex cams and stock IDS Webers. The Solex cams provide very nice power and torque throughout the entire RPM range all the way up to 7,000 RPM. But I prefer the S cams and will change the Solex cams out to S cams when I can afford it. As great as the Solex cam is the S cam has more character and fits the spirit of an early S car. (My opinion). Finally, there are supposed to be some very good aftermarket cams available...might be worth checking on them. Typically they have a more modern design than the older cams with more lift but less duration making them very good all around cams.